diff --git a/Timeline/Audio_File_SF.C b/Timeline/Audio_File_SF.C
index 8062f36..79cda35 100644
--- a/Timeline/Audio_File_SF.C
+++ b/Timeline/Audio_File_SF.C
@@ -33,6 +33,7 @@ Audio_File_SF::from_file ( const char *filename )
     SNDFILE *in;
     SF_INFO si;
 
+
     Audio_File_SF *c = NULL;
 
     memset( &si, 0, sizeof( si ) );
@@ -51,6 +52,7 @@ Audio_File_SF::from_file ( const char *filename )
 
     c = new Audio_File_SF;
 
+    c->_current_read = 0;
     c->_filename = strdup( filename );
     c->_length = si.frames;
     c->_channels = si.channels;
@@ -90,7 +92,10 @@ Audio_File_SF::close ( void )
 void
 Audio_File_SF::seek ( nframes_t offset )
 {
-    sf_seek( _in, offset, SEEK_SET );
+    if ( offset != _current_read )
+    {
+        sf_seek( _in, _current_read = offset, SEEK_SET );
+    }
 }
 
 /* if channels is -1, then all channels are read into buffer
@@ -103,22 +108,26 @@ Audio_File_SF::read ( sample_t *buf, int channel, nframes_t len )
 
 //    printf( "len = %lu, channels = %d\n", len, _channels );
 
+    nframes_t rlen;
+
     if ( _channels == 1 || channel == -1 )
-        return sf_readf_float( _in, buf, len );
+        rlen = sf_readf_float( _in, buf, len );
     else
     {
         sample_t *tmp = new sample_t[ len * _channels ];
 
-        nframes_t rlen = sf_readf_float( _in, tmp, len );
+        rlen = sf_readf_float( _in, tmp, len );
 
         /* extract the requested channel */
         for ( int i = channel; i < rlen; i += _channels )
             *(buf++) = tmp[ i ];
 
         delete tmp;
-
-        return rlen;
     }
+
+    _current_read += rlen;
+
+    return rlen;
 }
 
 /** read samples from /start/ to /end/ into /buf/ */
diff --git a/Timeline/Audio_File_SF.H b/Timeline/Audio_File_SF.H
index d43375e..1384ca8 100644
--- a/Timeline/Audio_File_SF.H
+++ b/Timeline/Audio_File_SF.H
@@ -27,6 +27,10 @@ class Audio_File_SF : public Audio_File
 
     SNDFILE *_in;
 
+    /* used to avoid unnecessary seeking--libsndfile isn't smart
+     * enough to do this for us */
+    nframes_t _current_read;
+
 public:
 
     static Audio_File_SF *from_file ( const char *filename );
diff --git a/Timeline/Disk_Stream.C b/Timeline/Disk_Stream.C
index 0c81a24..a554845 100644
--- a/Timeline/Disk_Stream.C
+++ b/Timeline/Disk_Stream.C
@@ -23,7 +23,8 @@
 #include "Port.H"
 
 // float Disk_Stream::seconds_to_buffer = 5.0f;
-float Disk_Stream::seconds_to_buffer = 1.0f;
+float Disk_Stream::seconds_to_buffer = 5.0f;
+// size_t Disk_Stream::disk_block_frames = 2048;
 
 /* A Disk_Stream uses a separate I/O thread to stream a track's
    regions from disk into a ringbuffer, to be processed by the RT
@@ -48,6 +49,9 @@ Disk_Stream::Disk_Stream ( Track_Header *th, float frame_rate, nframes_t nframes
 
     size_t bufsize = blocks * nframes * sizeof( sample_t );
 
+/*     const int blocks = 64; */
+/*     const size_t bufsize = (blocks * (nframes * sizeof( sample_t ))) + sizeof( sample_t ); */
+
     for ( int i = channels; i--; )
         _rb.push_back( jack_ringbuffer_create( bufsize ) );
 
@@ -151,6 +155,12 @@ Disk_Stream::io_thread ( void )
             for ( unsigned int j = i; k < _nframes; j += channels() )
                 cbuf[ k++ ] = buf[ j ];
 
+            while ( jack_ringbuffer_write_space( _rb[ i ] ) < block_size )
+            {
+                printf( "IO: disk buffer overrun!\n" );
+                usleep( 2000 );
+            }
+
             jack_ringbuffer_write( _rb[ i ], (char*)cbuf, block_size );
         }
     }
@@ -161,19 +171,39 @@ Disk_Stream::io_thread ( void )
 
 /* THREAD: RT */
 /** take a block from the ringbuffers and send it out the track's
- * ports */
+ *  ports */
 nframes_t
 Disk_Stream::process ( nframes_t nframes )
 {
-    const size_t block_size = _nframes * sizeof( sample_t );
+    const size_t block_size = nframes * sizeof( sample_t );
+
+//    printf( "process: %lu %lu %lu\n", _frame, _frame + nframes, nframes );
 
     for ( int i = channels(); i--;  )
     {
-        void *buf = (_th->output)[ i ].buffer( _nframes );
+
+        void *buf = _th->output[ i ].buffer( nframes );
 
         /* FIXME: handle underrun */
+
+/*         if ( jack_ringbuffer_read_space( _rb[ i ] ) < block_size ) */
+/*         { */
+/*             printf( "disktream (rt): buffer underrun!\n" ); */
+/*             memset( buf, 0, block_size ); */
+/*         } */
+/*         else */
+
         if ( jack_ringbuffer_read( _rb[ i ], (char*)buf, block_size ) < block_size )
-            printf( "disktream (rt): buffer underrun!\n" );
+        {
+            printf( "RT: buffer underrun (disk can't keep up).\n" );
+            memset( buf, 0, block_size );
+        }
+
+/*             /\* testing. *\/ */
+/*         FILE *fp = fopen( "testing.au", "a" ); */
+/*         fwrite( buf, block_size, 1, fp ); */
+/*         fclose( fp ); */
+
     }
 
     block_processed();
diff --git a/Timeline/Disk_Stream.H b/Timeline/Disk_Stream.H
index 52d987a..8efada0 100644
--- a/Timeline/Disk_Stream.H
+++ b/Timeline/Disk_Stream.H
@@ -49,6 +49,8 @@ class Disk_Stream
 
     sem_t _blocks;                                                /* semaphore to wake the IO thread with */
 
+//   volatile  nframes_t _seek_request;
+
     int channels ( void ) const { return _rb.size(); }
 
     Audio_Track * track ( void );
diff --git a/Timeline/Engine.C b/Timeline/Engine.C
index 26f5ef4..492e20e 100644
--- a/Timeline/Engine.C
+++ b/Timeline/Engine.C
@@ -62,7 +62,6 @@ Engine::process ( nframes_t nframes )
         return 0;
     }
 
-
     /* handle chicken/egg problem */
     if ( timeline )
         /* this will initiate the process() call graph for the various
diff --git a/Timeline/Mutex.H b/Timeline/Mutex.H
index 3d6eb3d..f98f9eb 100644
--- a/Timeline/Mutex.H
+++ b/Timeline/Mutex.H
@@ -30,7 +30,6 @@ public:
 
     Mutex ( )
         {
-//            _lock = PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP;
             pthread_mutex_init( &_lock, NULL );
         }
 
@@ -51,10 +50,10 @@ public:
             pthread_mutex_unlock( &_lock );
         }
 
-    int
+    bool
     trylock ( void )
         {
-            return pthread_mutex_trylock( &_lock );
+            return pthread_mutex_trylock( &_lock ) == 0;
         }
 
 };